Apparatus for dry sump lubrication of engines



E. A. Mom 2,456,886 APPARATUSA FR'DRY SUMP LUBRICATION 0F ENGINES 2Shets-Sheet 1 De.21,194s.

Filed Oct. 12, 1945 Dec. 21, 1948. E. A. MORI APPARATUS FOR DRY'SUMPLUBRICATION OF ENGINES 2 Sheets-Sheet 2 Filed Oct. 12, 1945 gvwQ/HMERNST A. MORI Patented Dec. 21, -1948 APPARATUS FOR DRY SUMP LUBRICATIONF ENGINES Ernest A. Mori, Pittsburgh, Pa., assignor to Gulf Research &Development Company, Pittsburgh, Pa., a corporation oi.' DelawareApplication October 12, 1945, Serial No. 621,886

(Cl. 18d-,6)

Claims. 1

This invention relates to improvements in 'engine lubrication systems o1the dry sump type. 'I'hese are so called because the oil supply, insteadof being retained in the crankcase as in conventional automobileAengines, is contained in a separate tank from which it is pumped tc theengine, and thence is continuously returned to the supply tank asrapidlyas it drains into the crankcase. Inasmuch as the crankcase issubstantially dry at all times the engine is not susceptible toi'iooding and fouling when operating in tiltedvpositions. whereasengines of conventional type in which the oil supply is selfcontainedmust operate in horizontal position, or one not departing greatly fromhorizontal, to avoid such eiiects. Engines embodying dry sumplubrication, therefore, have especial utility in lthe eld of aviationbecause they do not impose limitations on the maneuverability of anairplane.

In order to withdraw the oil normally draining to the crank case, aswell as to accommodate sudden surges tending to overrun the sump, thescavenge pump -is designed with a capacity of at least 21/4 times thenormal oil requirement of the engine. Fluctuating drainage of oil intothe sump may be due to any or all of several causes, such as variationsin engine speed, maneuvering of the airplane which requires the engineto assume changing positions and inclinations, and by intermittentactuation of hydraulic control devices drawing their supply of uid fromthe engine lubrication system, as for example mechanisms for changingpropeller pitch. Thus, since the scavenge pump must be designed with acapacity suilicient to keep the oil in the sump at a low level under alloperating conditions, the pump intake will at times be partly or whollyuncovered. As a result the scavenge pump sucks air or gas along with theoil during a considerable period of its operation, and the air becomesmechanically entrained in the oil returned to the supply tank, due inpart to the beater action of the pump on the oil-air mixture. Thispresents a hazardous condition, for at high altitudes the entrained vairbubbles expand in the intake side of the pressure pump supplying oil tothe engine due to the high ratio of absolute pressure in the oil supplytank to the absolute pressure in the pump gear teeth. AAt high altitudesthe flow of oil to the engineis reduced to the danger 'pointor'belowrdepen'ding upon the amount of air-entrainment,i since the oildelivery of the pressure pump is reduced -supply tank which permit inproportion to the volume of air present in the gear teeth.

Various expedients have been adopted to minimize or avoid airentrainment in the lubricating oil, mainly by mechanical means such asarrangements of ybaiiles and compartments in the the bubbles to separatefrom the body of oil. Another solution, and one of much practical value,is disclosed in the patent to Bruce R. Walsh, No. 2,373,360- Thiscomprises a main scavenge pump drawing from the bottom of the sump andof a capacity suflicient to keep the oil therein at a low level undernormal conditions, yet with its intake always and the auxiliary scavengewithout entraining air submerged, and an auxiliary scavenge pump drawingfrom a higher level, above the normal one, and separately delivering tothe upper part of the supply tank. Thus, the main scavenge pump handlesonly oil7 regardless of variations in the amount of oil draining to thecrankcase,

pump normally discharges air through a separate pipe into the supplytank above the oil level therein so that the air is vented to atmosphereWithout mixing with the oil, yet upon undue rise oi' oil in thel sumpthe auxiliary pump is primed and assists in discharging excess oil backto the supply tank to return the sump level to normal.

Such a system requires separate lines oi piping between the main andauxiliary scavenge pumps,v respectively, and the oil supply tank.Military necessity dictates that the amount of piping be reduced tominimize the chance that this vital part of the operating mechanism ofan airplane might be punctured by a bullet, and `in both military andcivilian use it is desirable to eliminate, in so far as possible, amultiplicity o! pipes which, if they should break, could cause acomplete failure of engine lubrication with disastrous' consequences.AIt is accordingly one of the principal objects of my invention toprovide a dry sump lubrication system which incorporates main andauxiliary scavenge pumps both of which deliver to an oil supply tankthrough the same` pipe, yet

in the oil so delivered, lrrespective of a iluctuating oil level in thesump. Other and further objects will be evident from the followingdescription and drawings, in which: Figure l is a partly diagrammaticview of one form of my invention embodying main and auxiliary scavengepumps, and pressure pump, inline.

lFigure'i-is also a. partly diagrammatic view' -of a modifiedarrangement wherein the main tank over the curved scavenge pump ismounted inside the engine crankcase and is driven by a shaft geared tothe main drive shaft for the auxiliary scavenge pump and the pressurepump.

Referring more particularly to the drawings and rst to Figure l thereof,an engine crankcese I is provided with a sump il inits bottom to receiveoil draining from the engine bearings. The oil for lubrication isdelivered from tank i2, through pipe i3 and pressure pump IS, and thencethroughY pipe i5 to the engine. A main scavenge pump IB and an auxiliaryscavenge pump il are mounted in line with the pressure pump it, andl allare directly driven by shaft le which projects through the crankcase.The inlet pipe I9 of the main scavenge pump extends into sump ii at alow point, below the normal oil level 2li whereas the inlet pipe 2i oithe auxiliary scavenge pump terminates in the sump above the normallevel, as indicated at 22.

The main scavenge pump discharges through pipe 23 and through either theupper or lower branch pipes 26 and 25 to the top or bottom of the supplytank, depending upon the position of the two-wayy valve 26. Thus, duringthe warm.- up period for the engine, oil returned to the supply tank maybe directed through the lower adjacent to the inlet of pipe i3, wherebymore direct circulation Following the initial warm-up period it isusually desirable to adjust valve 2t so that oil returning to the supplytank hows through the upper branch where heat may be extracted Iby aheat exchange cooler 2l prior to its discharge into the surface ofbaille 28 which assists in eliminating any air bubbles from the sheet ofoil flowing thereover, and avoids agitation of the main body of oil suchas would cause bubbles of air to form in it.

At extremely high altitudes the effect of the will open and permit theoil to take an alternative path by-passing the cooler.

Any sudden surge of oil collecting in the 'sump and tending to overrunit is drawn by pipe 2i into the auxiliary scavenge pump and dischargedpipe 3d into the stream from pump. When this occurs the single pipe 28serves both main and auxiliary scavenge pumps.` Normally, however, sincethe inlet of the auxiliary scavenge pump is entirely pump only air. Forreasons out it is undesirable to mix air with the main oil stream. Myinvention, therefore, provides a spring-pressed check Valve 8i of two orthree pounds pressure in the branch pipe 36and a restricted lbleedertube 32 between the auxiliary scavenge pump and check valve, andiesirably near the check valve, leading back into the crankcase. So longas the intake of the auxiliary scavenge pump is uncovered, air which ispumped will merely be discharged back to the crankcase through thebleeder tube, since its pressure will be insulcient to overcome thepressure of oil behind the check valve plus the spring pressure tendingto hold the valve closed. If the oil should rise in the sump to thelevel 22, or higher, the auxiliary scavenge pump will immediately primeitself because of the air vbleed in the dis,l charge side, and thereuponthe check valve will* the auxiliary oil stream will join but will bediscontinued abruptly open so that the main one when a low level isrestored in the sump.-

of the warm.oil is obtained.

iat

engine and a pressure TheA assembly of vFigure 2 is similar in itsoperation. Here, however. the main scavenge pump 33 is mounted insidethe crankcase andy is driven by a short shaft 3i connected to the driveshaft 36 by bevel gearing 36. As in the previously described embodiment,the main scavenge pump discharges through a pipe 31 to a supply tank 38.through either an upper branch 39 or a lower branch lid, controlled by atwo-way valve 4|. Here, also. the upper branch has a cooler 42 and valvecontrolled lay-pass A33, while the lower branch entering the tank opensadjacent to the pipe M which supplies the pressure pump d5.

The connection between' the auxiliary scavenge pump it and the main oilline, as shown, comprises a short connecting pipe t? in which a springpressed check valve il@ is mounted and which normally closes thepassage. Thus. when the intake pipe di) of the auxiliary scavenge pumpis uncovered, air which is pumped cannot enter the main supply pipe andtherefore passes back to the crankcase through a small bleeder tube 50which communicates with the pipe di between the auxiliary scavenge pumpand the check valve. When the oil in the sump rises suiciently, to bepicked up by the auxiliary scavenge pump, however, the check ,valve willopen under the increased pressure exerted on it and the auxiliaryoilstream will thereupon join the main stream as the same is discharged bythe main scavenge pump. In both this and the preceding embodiment it isto be noted. that the bleeder tube is of such small bore that althoughair is effectively vented back to the crankcase, only a negligibleamount of oil can return by this route, due to greater resistance to thepassage of the more viscous liquid, so that this discharge of oil fromthe auxiliary scavenge pump into the main oil stream is not appreciablyreduced.

What I claim is:

l.` A dry sump lubrication system for engines comprising an oil supplytank separate from the engine and a pressure pump delivering oiltherefrom to the engine, a main scavenge pump having an inlet which issubmerged in oil retained in the engine sump. an auxiliary scavenge pumphaving an inlet which is norm-ally. above the level of oil in the sump,a common discharge pipe for both the main and auxiliary scavenge pumpsleading to said supply tank, a valved connection between the dischargeof said auxiliary scavenge pump and said common discharge pipe, andmeans for bleeding oi air which is normally pumped by said auxiliaryscavenge pump.

2. A dry sump lubrication system for engines comprising an oil supplytank separate from the pump delivering oil therefrom to the engine, .amain scavenge pump having an inlet which is submerged in oil retained inthe engine sump, an auxiliary scavenge pump having an inlet which isnormally above the level of oil in the sump, a common discharge pipe forboth the main and auxiliary scavenge pumps leading to said supply tank,a valved connection between the discharge of said auxiliary scavengepump and said common discharge pipe normally closing communicationtherebetween when said auxiliary scavenge pump discharges air butadapted to establish communication therebetween when oil is pumped, andbleeder meansfor relieving air pumped by the auxiliary scavenge pumpwhen the vvalved connection closes communication with the commondischarge pipe.

3. In a dr'y sump lubrication system including Y main and auxiliaryscavenge pumps drawing from audace different levels in the enginecrankcase and dissure pump returning oil from the supply tank to the`engine, the improvement comprising a. com mon discharge pipe for boththe main and auxiliary scavenge pumps leading to said supply tank, avalved connection between the discharge of said auxiliary scavenge pumpand said common discharge pipe adapted to establish communicationtherebetween only when oil is being delivered by said auxiliary scavengepump, and a bleedeifor air pumped by said auxiliary scavenge pump whencommunication with said common discharge pipe is blocked.

4. A dry sump lubrication system for engines comprising an oil supplytank separate from the engine and a pressure pump delivering oiltherefrom to the engine, a main scavenge pump drawing oil from theengine crankcase at a low point therein, an auxiliary scavenge pumpdrawing from a higher level normally above any accumulation of oil inthe crankcase, a common discharge pipe for said main and auxiliaryscavenge pumps communicating with said supply tank, a connecting pipebetween the outlet of said auxiliary scavenge pump and said commondischarge pipe, a check valve therein adapted to open under pressure ofliquid discharged by said auxiliary scavenge pump and a bleeder tubecommunicating with said connecting pipe between the outlet oisaidauxiliary scavenge pump and said check valve.

5. A dry sump lubrication system for engines comprising an oil supplytank separate from the engine and a pressure pump delivering oiltherefrom to the engine, a main scavenge pump drawing oil from a sump inthe engine erankcase and having an inlet'which is continuouslysubmerged, an auxiliary scavenge pump drawing from a higher level.normally above the oil level in the 'charging to a separate supply tank,and a pres- 4 sump, a common discharge pipe for both the main andauxiliary scavenge pumps leading to said supply tank, a connectionbetween the discharge of said auxiliary scavenge pump and the saidcommon discharge pipe, a spring-pressed check valve in said connection,said check valve being normally closed when air is discharged .by saidauxiliary scavenge pump, and means providing a restricted passageextending from said connection at a point adjacent said check valve atthe uP- stream side thereof to relieve air discharged from saidauxiliary pump during normal operation, said check valve opening andestablishing communication between said auxiliary scavenge pump andcommon discharge pipe at such times as the inlet of the auxiliaryscavenge pump becomes submerged in oil and the auxiliary scavenge pumpprimes itself due to the presence of the restricted passage between Vthepump and check valve ,through which passage the pump can exhaust Itheair entrapped in its pumping members, due -to .the oil submergenee atthe inlet. l

` ERNEST A. MORI.

REFERENCES CITED i The vfollowing references are of record in the illeof this patent:

UNITED STATES PATENTS

